DESCRIPTION: The S. gordonii glucosyltransferase (GTF) enzyme synthesizes glucans that can influence the accumulation of bacteria in the developing Dental plaque biofilm. The working hypothesis of the ongoing project (DE 11090) is that regulation of GTF activity in S. gordonii involves complex molecular interactor(s) that may have ecological implications for bacterial colonization and survival in the oral cavity. The goal of this ongoing project is to investigate the environmental signals and molecular mechanisms that regulate glucosyltransferase expression in the commensal species, S. gordonii. The Specific Aim of the proposed studies described in this Supplemental Application, is to use DNA microarrays to identify and characterize coordinately regulated genetic networks associated with expression of the GTF structural gene, gtfG and its positive regulatory determinant, rgg. Gone expression profiles of the parent strain will be compared to strains in which genes involved in GTF activity (e.g. rgg and gtfG) have been specifically inactivated. The proposed experiments will also examine gene expression in these bacterial strains under specific environmental conditions, which influence the level of GTF activity. Microarray methodology will allow an essentially genome-wide, highly sensitive search for coordinately expressed genes. The results obtained will be validated using quantitative real-time polymerase chain reaction (PCR). Construction of microarrays for these proposed studies will be facilitated by the use of existing DNA clone sets available from the parental strain Challis used in the S. gordonii sequencing project; these molecular tools were not available at the time of the original parent grant application. For this Supplemental Application, microarray experiments will be focused on addressing the working hypothesis of the parent grant. The results of the proposed supplemental studies will be used specifically to accelerate and supplement ongoing genetic and functional studies in the parent grant. These studies are designed to unravel the complex mechanisms involved in regulation of GTF expression in S. gordonii and elucidate the contributions of the synthesized glucans to the biology of Dental plaque. [unreadable] [unreadable]